Can I apply for an officer role in the British Armed forces after joining as a soldier ?

If you enlist then you can apply for a commission, although it is not the orthodox path it is not uncommon. A traditional route is after completing bewteen 20-22 years service and gaining an LE (late entry commission). You can be reccommended before then at both Private and Lance Corporal/Corporal level and I know af quite a few officers who have done this. The best way however is to apply for a commission straight away.